can_higher_layer_protocols:what_is_wrong_with_rtr

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===== Why using RTRs is not advised in CANopen? =====

RTR means //Remote Transmission Request// - a CAN frame requesting another node to send a requested frame.

CiA, especially the Special Interest Group CANopen is not recommending using RTR Messages. You may ask: why?

The CiA has a paper explaining the contras and giving advice for better solutions. CiA 802 V1.1.0: CANopen application note - CAN remote frames: Avoiding of usage (IGCO_802v01010000.pdf) \\ It can be downloaded free of charge after a registration at  [[http://www.can-cia.org/standardization/specifications/| CiA specifications]]. 
 
In short the main topics:

    * The number of transmit messages buffers supporting CAN remote frames is limited on most so-called [[:can_faq_basic_full| Full CAN]] controllers.
    * Implementation of a CAN driver handling RTR is much more complex. On some controllers impossible.
    * Some CAN controllers react different on the 'data length' code in the RTR frame and the data frame. This is due to differences in the CAN implementation.  \\

Trace: • xanbus • sds • vscp • devicenet • canopen • j1939 • can_interface_api • ethernet • canmd • can_higher_layer_protocols_uavcan

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